Reforming process



Sept. 26, 1961 H. w. GROTE 3,001,928

REFORMING PROCESS Filed Aug. 7, 1959 l F racf/ ana/or TTR/VEYS:

United we,

3,001,928 REFRMING PROCESS Henry W. Grote, Hinsdale, Ill., assignor toUniversal Gil Products Company, Des Plaines, Ill., a corporation ofDelaware l Filed Aug. 7, 1959, Ser. No. 832,887 9 Claims. (Cl. 20S-65)The present application is a continuation-impart of my copendingapplication, Serial Number 563,075, led February 6, 1956, as acontinuation-impart of application, Serial Number 277,980, filed March22, 1952, and application Serial No. 478,968, tiled December 31, v1954,all of said earlier applications being now abandoned.

The presen-t invention relates, in its most broad scope, to a novelmethod for obtaining high yields of aromatic hydrocarbons from varioushydrocarbon mixtures and fractions. More specifically, the invention isdirected toward an integrated, two-stage catalytic reforming processwhich affords high yields of aromatic hydrocarbons while converting anotherwise low-octane parainic hydrocarbon into its` high-octane isomerand providing for the removal thereof from said integrated process.

Recent developments in the automotive industry have greatly increasedthe demand for possessing unusually high octane ratings, and thepetroleum industry has been striving constantly to keep up with thesedemands. One process that has achieved Widespread commercial lacceptanceis the catalytic reforming process. .The usual method of eectingcatalytic reforming of straight-run gasoline or a straight-run gasolinefraction, inorderto produce aromatics and other high octanev gasolinecomponents, suitable for aviation and motor fuels, lsuffers from thealmost impossible .task of obtaining complete dehydrogenation andarornatization ofthe naphthenic hydrocarbons, within the particularlychosen charge stock, to aromatics; for example, the conversionof'substa'ntially all the cyclohexane and methylcyclopentane to benzene.Also, it is not generally possible by conventional methods to-convertany substantial proportion of the straight chain parafns to aromatics bydehydrocycliza-tion, or to iso-paraflins by isomeriza-tion, as forexample, the, conversion of normal hexane to benzene, ortofiso-hexane.There has recently been disclosed, and provided ,commercially, animproved reforming operation which utilizes a platinum-alumina-com'binedhalogen 'catalyst under conditions that permit extended periods'ofcontinuous operation without the necessity of regenerating or replacingthe catalyst, providing thereby a substantially non-regenerativeprocess. This improved catalyst yand operation has been set forth .in apatent to Vladimir 2 and which permits obtaining high octane productssuita-. b-le for aviation as well as motor fuels.

It is a particular object of the present invention to provide anintegrated process with means for convertingv six-carbon atomhydrocarbons into isoparaflins and benzene while affording a method forthe recovery of isoparafiins from the process, avoiding thereby thedestruction of a substantial portion thereof.

In its most broad embodiment, the present invention relates to a processwhich comprises catalytically reforming a gasoline fraction at apressure of from about 200 to about 1000 pounds per square inch,separating from the resultant products a low-boiling fraction containingisohexane and lighter hydrocarbons and a heavier fraction containingaromatics, normal hexane nad five-membered ring naphthenes, subjectingsaid heavier fraction to solvent extraction fto separate the aromaticstherefrom, and catalytically reforming the remaining non-aromaticrafnate, comprising normal hexane and live-membered ring naphthenes, ata pressure at least 75 pounds per square inch lower than that in therst-mentioned reforming'step to form a product containing additionalaromatics and isohexane.

In another embodiment, the present invention relates to a process foreffecting an improved yield of aromatic hydrocarbons from a hydrocarbonstream boiling within the gasoline boiling-range which comprisessubjecting said stream and hydrogen to reforming in the presence of acatalyst that promotes dehydrogenation of naphthenes and hydrocrackingof parains, subsequently cooling the resulting reformed stream andeffecting the separation thereof to provide a gaseoushydrogen-containing stream and an Varomatic-rich hydrocarbon stream,passing the latter toa fractionating zone and removing normally gaseouscomponents therefrom, treating the remaining fraction in a separationzone, withdrawing from said separationzone a fraction containing asubstantial portion of aromatics an'd a second fraction containing alarge proportion of parainic hydrocarbons, subjecting at least a portionof said second fraction to contact with a dehydrocyclization catalyst inthe presence of hydrogen and effecting the conversion thereof to formadditional aro- Haensel, Patent No. 2,479,110, issued August 16, 1949.

However, in connection with this improved reforming process it isgenerally desirable to process full boiling range gasoline or gasolinefractions at -a pressure within the range of from about 400 to 1000pounds per square inch to insure a substantially non-regenerativeoperation with. a minimum of carbon formation and the resulting catalystdeactivation.. At this Ihigh pressure level, .the conversion of variousof the naphthenic hydrocarbons, more specially the lower boilingnaphthenes to aromatics and the parati-ins to aromatics, is limited, asset forth hereinabove, and therefore, there is not obtained a maximumproduction of aromatics.

lt is, therefore, the principal object of the present invention toprovide an improved combined operation effooting a high yield ofaromatics from a hydrocarbon fraction boiling lwithin the gasolineboiling range.v

lt is also an object of the invention to provide a multiple-stageoperation which is particularly suitable for the 7 production ofaromatics from naphtheneshand parains matic hydrocarbons, separating the-resulting stream to provide a gaseous hydrogen stream and a hydrocarbonstream and recycling at least a portion of the latter stream to the rstmentioned fractionating Zone. In a more specific embodiment, the presentinvention relates to a reforming process which comprises subjectinggasoline to catalytic aromatization at a pressure in excess of about 500pounds per square inch, fractionating theresultant hydrocarbon productsin a fractionating zone to separate isohexanes and lighter hydrocarbonsboiling below about F. from normal hexane and heavier hydrocarbons,subjecting said normal hexane and heavier hydrocarbons tosolventextraction to separate aromatic hydrocarbons from non-aromatichydrocarbons, recovering the separated aromatics, fractionating saidnon-aromatic hydrocarbons in a second fractionating zone to separatetherefrom a C6 hydrocarbon fraction having an atmospheric boiling rangeof from about 150 F. to about F. and containing five-membered ringnaphthenes, subjecting said C6 fraction to catalytic isomerization andaromatization at a pressure below about 300 pounds per square inch toform additional aromatic hydrocarbons and isohexanes, supplying theresultant hydrocarbon conversion products to the first-mentionedfraction-ating zone for fractionation therein Itogether with thefirst-mentioned hydrocarbon products, and recovering as an overheadproduct from said first-mentioned fractionating zone lthe commingledisohexane and lighter hydrocarbons boiling below about 150 F.

vIn its most specific embodiment, the present invention provides acatalytic reforming process which comprises subjecting a gasolinefraction to reforming at a temperature of from about 600 F. to about1000 F. and a pressure of from about 500 to about 800 pounds per squareinch, with hydrogen at a hydrogen to hydrocarbon mol ratio of from about5:1 to about 20:1, said conditions in the reforming zone being selectedto minimizc the production of olenic hydrocarbons, in the presence of acatalyst comprising alumina, 0.01% to about 1% by weight of platinum andfrom about 0.1% to about 3% by weight of combined halogen, subsequentlycooling the resultant reformed stream and eiecting the separationthereof to provide a gaseous hydrogen-containing stream and anaromatic-rich hydrocarbon stream, introducing said aromatic-rich streamto a first fractionating zone to remove normally gaseous componentstherefrom, passing the remaining aromatic-rich hydrocarbon stream fromthe first fractionation zone to a second fractionation zone andfractionating said stream to separate a low-boiling stream containingisohexanes and lighter hydrocarbons, having a boiling point below about150 P., from the aromatic-rich portion of said stream, passing theresulting fractionated aromatic-rich stream from the secondfractionation zone to an extraction zone wherein said stream iscountercurrently contacted with a selective solvent containingdiethylene glycol and from about 2% to about 30% by weight of water,separately removing from said extraction zone an extract streamcontaining said solvent and a substantial amount of the aromatics insaid portion, and a rainate stream containing a substantial amount ofparainic hydrocarbons, introducing said extract to a stripping column,removing as overhead from said column an aromatic-containing stream,removing as bottoms from said column a solvent stream and recycling saidstream to said extraction zone, fractionating said raliinate to separatetherefrom a C6 hydrocarbon fraction having an atmospheric boiling rangeof from about 150 F. to about 185 F. and containing tivernembered ringnaphthenes, subjecting said C@ fraction together with hydrogen tocontact with a dehydrocyclization catalyst at a pressure below 300pounds per square inch, effecting thereby the conversion thereof to formadditional aromatic hydrocarbons, separating the resulting stream toprovide a gaseous hydrogen-containing stream and a hydrocarbon streamand recycling at least a portion of this latter stream to the firstfractionation zone.

Briefly, the present invention provides a method for effecting animproved yield of aromatic hydrocarbons from a hydrocarbon streamboiling substantially within the gasoline range which comprisessubjecting the hydrocarbon stream to reforming in the presence ofhydrogen and a suitable reforming catalyst. In the rst reforming zone,the principal reactions are those by which naphthenes are dehydrogenatedto aromatics, and the heavy paraflins are hydrocracked to lower-boilingparaftins. It is also preferred that the conditions and catalyst in thefirst reaction zone be such that the catalyst will also exhibit asignificant degree of isomerization and dehydrocyclization activity.Therefore, the catalyst preferably isomerizes normal paraflins toisoparatiins and converts C, hydrocarbons containing tive-membercd ringnaphthenes to aromatics. The resulting reformed stream is cooled and aseparation thereof effected to provide a gaseous hydrogen-containingstream and an aromaticrich hydrocarbon stream containing paraflinichydrocarbons. The aromatic-rich hydrocarbon stream is fractionated toreject the normally gaseous hydrocarbons produced in the process and theresultant liquid is further fractionated to separate a low boilingstream containing isohexane and lighter hydrocarbons from thearomaticrich portion of the stream. Therefore, the reformed efuentstream from the reaction zone is fractionated to separate a low boilinghydrocarbon stream, having a boiling point below about 150 F. andcontaining isohexanes and lighter hydrocarbons, from the aromatic- 4rich portion of the stream. The aromatic-rich portion of the stream,containing normal hexane and higher boiling paratiins and aromatics, ispassed to an extraction zone in which the recovery of aromatichydrocarbons is effected. At least a portion ofthe resultingnon-aromatic or paratnic hydrocarbon stream from the extraction zone ispassed to a second reforming zone wherein it is contacted with acatalyst having dehydrocyclization, aromatization and isomerizingactivities while in the presence of hydrogen. In a specific embodimentof my invention the non-aromatic hydrocarbon stream from the extractionzone is passed to a fractionation zone and fractionated to provide agasoline stream boiling above about 185"a F. and a C-hydrocarbon streamhaving an atmospheric boiling range of from about 150 F. to about 185 F.This latter C-hydrocarbon fraction is passed to the second reformingzone wherein it is contacted with a catalyst having dehydrocyclization,aromatizing, and isomerization activities, while in the presence ofhydrogen. The second reforming zone is at pressure at least pounds persquare inch lower than the first reforming zone and preferably at leastpounds per square inch lower than the pressure in the first reformingzone. In one specific mode of operation, the pressure in the rstreforming zone is in excess of 500 pounds per square inch gauge and thepressure in the second reforming zone is below about 300 pounds persquare inch gauge. Generally the pressure in the first catalyticreforming zone is within the range of from about 500 to about 800p.s.i.g. and the pressure in the second catalytic reforming zone isbelow about 300 p.s.i.g. In the second reaction zone the temperature ispreferably higher than the temperature in the iirst reforming zone Theproduct from the second reaction zone is passed to the firstfractionation zone and from there the stream follows the same route asthe effluent from the first reforming zone.

A feature of my process is that mild hydrocracking conditions may beemployed in the first reforming step. Generally more severe conditionsare necessary to dehydrocyclicize a straight chain parain to form anaromatic, than to dehydrogenate a cycloparatiin or naphthene to form anaromatic hydrocarbon. Reforming of the low-octane number paratlins in aseparate reaction zone results in their being dehydrocyclicized toaromatics and/or their being converted to lower boiling high octanenumber parains without the excessive production of gaseous hydrocarbonsthat would result were these higher boiling paratiins substantiallycompletely reacted in the rst reforming reactor continued at conditionsof high severity. Therefore, a feature of my process is that theconditions in the second reforming zone may be severe enough to converta substantial portion of the parafns to aromatics while at the same timeminimizing undesirable side reactions which otherwise reduce yields ofuseful gasoline products. As hereinbefore set forth, one of the majorcauses of excessive coke deposition, which inherently results in rapidcatalyst deactivation, is the reaction of various aromatic hydrocarbonsto form heavy, carbonaceous polynuclear aromatics. Excessive carbondeposition is also facilitated through the accumulation of certainparainic hydrocarbons which, in a process employing recycle of a portionof the reaction products, either pass unaffected through the reactionzone, or react in a detrimental manner to form coke and othercarbonaceous material. In my process, however, the aromatic hydrocarbonsare withdrawn in a substantially pure stream through the use of asolvent extraction procedure, and a provision is made whereby theparalinic hydrocarbons are converted to a valuable product and alsowithdrawn from the process.

High severity operation, in the presence of aromatics, is also notdesirable from considerations of the chemical equilibria involved, as insuch operations the aromatics in the feed limit the extent to which sucharomatics can be formed from naphthenes and paraiins. In contrast,however, the use of my process involves the removal of a substantialportion of the aromatics from the charge to the reaction zone which thuspermits the formation of additional aromatics unrestricted by thelimitations of chemical equilibria. Similarly, the isomer-ization of lowoctane number rating straight chain paraflins to higher octane qualitybranched chain structure paraffins is -an equilibrium chemical reaction.As the isomerization of normal hexane is important to achieve inupgrading gasolines, due to the very limited extent that it undergoesdehydrocyclization at reasonable operating conditions, a feature of myprocess 4is that .high-octane isohexanes may be continuously removed,and the normal hexane recycled to the reaction zone in the raffinatethus obtaining substantial conversion of low octane normal hexane tomuch higher quality isohexanes, accompanied by almost no restrictions inyield due to chemical equilibrium considerations. Accordingly, thearomatics are separated from the parafns and naphthenes in the reformatefrom the first reaction zone for several reasons. One reason is that ifthe aromatics were introduced to the second reaction zone, there Wouldresult a lower overall yield of reformate, presumably due to theconversion of the aromatics to gaseous hydrocarbons and to hydrocarbonsboiling above the gasoline range, primarily polynuclear aromatics.Another reason is that high concentrations of aromatics in the reactionzone tend to result in a greater carbon deposition and consequently-ashorter catalyst life. Still another reason, which has hereinbefore beenmentioned, is that high concentrations of aromatcs in the reaction zonetend to suppress the dehydrogenation of naphthenes to aromatics and tosuppress the dehydrocyclization of parains to aromatics, saiddehydrogenation and said dehydrocyclization beingequilibrium reactions.By eliminating low octane number, high boiling paraflins from the finalproduct the end product is a reformate of high quality even though thelow boiling portions of the charging stock have never been subjected tothe relatively severe operating conditions that previously have beenthought to be necessary to produce high quality reformate.

Similarly, the reaction products from the first reaction zone aresubjected to a sep-aration to remove therefrom the normally gaseoushydrogen-containing stream which is recycled to the reaction zone, andthose normally liquid, low-molecular weight hydrocarbons boiling belowabout 150 F., and which hydrocarbons are rich in isohexane. Therem-aining reaction products are then subje'cted to a solvent extractionprocedure to effect removal of the aromatic hydrocarbons, and to providea raflinate 'stream containing normal hexane and five-membered ringnapthenes. The rainate is fractionated to produce a particularhydrocarbon fraction having an atmospheric Iboiling range of about 150F. to about 185 F. and rich in normal hexane and the five-membered ringnaphthenes. This hydrocarbon fraction is passed into a separatelydistinct reforming zone to effect the formation of additional aromaticsand to convert the normal hexane into high-octane isohexane. Theresulting product is recycled to combine with the reaction product fromthe first-mentioned reaction zone, and the -additional isoh'exane issubsequently removed from the process with those low molecular weighthydrocarbons boiling below 150 F., the additional aromatics'beingremoved wia the solvent extraction procedure, In this manner, the normalhexane can be advantageously utilized to produce isohexane, and thelatter is not permitted to accumulate within the process, nor is itsubject to detrimental cokefo-rming reactions.

The charge stocks which may be reformed, in accordance with my process,comprise hydrocarbon fractions that boil Within the gasoline range andcontain naphthenes and parains. The preferred stocks are thoseconsisting essentially of naphthenes and parans, although aro- 6matics'and :minor amounts of oletins may be presenti This preferredclass includes straight-run gasoline, natural gasoline and the like. Thegasolinefraction may be a full boiling range gasoline having an initialboiling point within the range of from about 50 F. to about,l F. and anend boiling point within the range of from about 350 F. to about 425 F.or it may be aselected fraction thereof which usually is a higherboi-ling` fraction commonly referred to as naphtha, having an ini-A tialboiling point within the range of from about F. to rabout 250 F. and anend boiling point within the range of from about 350 F. to about 425 F.Mixtures of the various gasolines and/or gasoline fractions may also beused, and thermally cracked and/or catalytically cracked gasolines maybe employed. However, when these unsaturated gasoline .fractions areused, it is preferred that they be used either in admixture with astraight-run or natural gasoline fraction, or else hydro-- gneated priorto use.

In a preferred operation in the iirst reforming step, wherein the chargeis subjected to hydrocracking and aromatization, the catalytic contactis made at a pressure of from about 200 to about 1000 pounds per squareinch. -In the subsequent catalytic contacting step, the C8 plushydrocarbon fraction contacts the catalyst at a lower pressure, saidpressure being at least 75 poundsY per square inch and preferably atleast 100 pounds per square inch lower than the pressure in the firstreform-1 ing step. It is also to be noted that certain of thefivemembered naphthenes, such as methylcyclopentane, are not completelyconverted to benzene in the first reform-v ing step so that a subsequentcontact after removal of aromatics permits Ifurther dehydrogenation andconversion of such fractions to benzene and other arom-atics while thenormal hexane fraction is subjected to dehydrocyclization to producearomatics of higher octane number, and isomerization to isohexane andother branched parains of higher octane number. -It is also a feature ofthe improved operation to effect the recycling of the resultnighydrocarbon stream after contact with a dehydrocyclization catalyst, sothat resulting aromatics land isohexanes are admixed with the reformedstream' entering the first fractionation zone. In the firstfractionation zone, the normally gaseous components are taken offoverhead and the remaining stream is passed to a second fractionationzone wherein isohexanes and lighter hydrocarbons boiling below 150 F.are taken oif overhead and removed as such. i

A preferred operation effects the recycle of the hydrogen stream beingseparated `from the reformed gasoline stream into contact with thecharge stream in order to provide added hydrogen to the catalyticreforming zone.l Similarly, hydrogen separated from the second stagedehydrocyclization zone may ibe recycled to the latter to provide thepresence of additional hydrogen during the catalytic contact of theparains.

Various types of desirable 4and suitable catalystsV may be utilizedwithin each stage of theprocess, however, the preferred operationutilizes the improved platinumalumina-combined halogen catalyst in eachof the contact zones. The catalysts that may be used in the first re-`forming zone of my invention comprise thosereforming catalysts thatpermit dehydrogenation of naphthenic hydrocarbons, hydrocracking ofparainic hydrocarbons and isomerization of parainic hydrocarbons. Asatisfactory catalyst comprises a platinum-alumina-silica catalyst ofthe type described in U.S. Patent No. 2,478,916, issued August 16, 1949.A preferred catalyst is the type described in U.S. Patent No. 2,479,109,issued August 16, 1949. Other catalsts such as molybdena-alumina,chromia-alumina and platinum on a cracking catalyst base may be used. Inthe second reforming zone, as well as in the first reforming zone, theplatinum concentration in the catalyst may range up to about 10% byYWeight or more of the alumina, but a desirable catalyst may be.

provided to contain as low as from `about 0.01% to about 1% by weight ofplatinum. The halogen ions may be present in an amount of from about0.1% to about 8% Yby weight of the catalyst but preferably are presentin an amount of from Iabout 0.1% to about 3% by weight of the alumina ona dry basis. Also, while any of the halogen ions provide a desirablecatalyst, the uoride ions'are particularly preferred and next in orderare the chloride ions, the bromide ions and iodide ions. In the secondstage of catalyst contact, wherein the non aromatic Ca-plus fractionundergoes dehydrocyclization, and wherein C8 hydrocarbons containinglivemembered ring naphthenes undergo isomerization and dehydrogenation,there may be a lesser quantity of platinum present in the catalyst.

Except for pressure level, the operating conditions maintained in eachof the two reforming zones of my process are essentially the same.Generally the pressure in the rst reforming zone is within the range offrom about 200 to about 1000 p.s.i.g. and the pressure in the secondreforming zone is at least 75 p.s.i. lower. Genorally the pressure inthe rst reforming zone is in excess of 500 p.s.i.g. and the pressure inthe second reforming zone is below about 300 p.s.i.g. More specically,the pressure in the iirst reforming zone is within the range of fromabout 500 to about 800 p.s.i.g. and the pressure in the second reformingzone is from about 25 p.s.i.g. to about 300 p.s.i.g. The conditions inthe rst zone should be such that substantial conversion of naphthenes toaromatics, and relatively mild hydrocracking of parans are induced, andfurther the operating conditions in the second zone should be such thatthere is a substantial conversion of parafflnic compounds to lomtics bydchydroyclization as well as isomerization of paramos such as theisomerization of normal hexane to isohexane. When employingplatinum-alumina-combined halogen catalyst in both of the reformingzones, the conditions in cach are usually a temperature within the rangeof from about 600 l?. to about 1000" F., and a weight hourly spacevelocity of from about 0.5 to about 20. The weight hourly space velocityis defined as the weight of Oil per hout per weight of catalyst in thereaction zone. It is preferred that the reforming reaction in both ofthe reaction zones be conducted in the presome of hydrogen. In oneembodiment of the process, sucient hydrogen Will be produced as a resultof the various reactions to furnish the hydrogen required in theprocess, and, therefore, it may be unnecessary to introduce hydrogenfrom an extraneous source or to recycle hydrogen within the process.However, it will be preferred to introduce hydrogen from an extraneoussource generally at the beginning of the operation and to recyclehydrogen within the process in order to be assured of a sucient hydrogenatmosphere in each of the reaction zones. The hydrogen present in eachof the reaction zones will be within the range of from about 0.5 toabout 2() mols of hydrogen per mol of hydrocarbon. In some cases, thegas to be recycled will contain hydrogen sulde introduced with thecharge or liberated by the catalyst, and it is within the scope of thepresent invention to treat the hydrogen-containing gas to removehydrogen sulfide or other impurities before recycling the hydrogen tothe reforming zone. The pressure in the first reaction zone is fromabout 200 to about 1000 pounds per square inch. The pressure in thesecond reaction zone is lower, and is at least 75 pounds per square inchlower and preferably at least about 100 pounds per square inch lower.The temperature in the second reaction zone is preferably higher thanthat employed in the rst reaction zone. The conditions are furtherselected that there are substantially no olens present in the productstreams from the tirst and second reaction zones.

The eluent from the rst reforming zone is usually passed to a stabilizerwhich elects a separation of the normally gaseous material whichcomprises hydrogen; hydrogen sulfide, and hydrocarbons containing from 1to 4 carbon atoms per molecule from the normally liquid hydrocarbons.rthe liquid from the stabilizer is then passed to a fractionation zonewhich effects separation of isohexane and lighter hydrocarbons havingboiling points below about F. from the liquid charge. The doohexanzedhydrocarbon stream is then passed to an extraction z one to produce amore concentrated aromatic fraction.

Solvent extraction processes are utilized to separate certain desiredcomponents in a mixture from the other components thereof by aseparation based upon u dfference in solubility of the components in aparticular solvent. It is frequently desirable to separate varioussubstances by solvent extraction; for example, when the Substances to beseparated have similar boiling points, arc unstable at temperatures atwhich fractionation is cffected, forrn constant boiling mixtures, ctc.It is particularly desirable to separate aromatic hydrocarbons rom apetroleum fraction containing these aromatic hydrocarbons by solventextraction because a petroleum fraction is normally a complex mixture ofhydrocarbons whose boiling points are extremely close together andbecause the petroleum fraction contains numerous cyclic compunds whichtend to form constant-boiling or azeotropic mixtures. As hereinbeforestated, the basis of a solvent extraction separation is the differencein solubility in a given solvent of one of the substances to beseparated from the other. It may, therefore, be seen that the moreextreme this difference the easier the separation will be and an easierseparation reflects itself processwise in less expensive equipment andgreater yields per pass in the use of processing equipment as well as inhigher purity of product.

A particularly preferred solvent for separating aromatic hydrocarbonsfrom non-aromatic hydrocarbons is a mixture of water and a hydrophilicorganic solvent. Such a solvent may have its solubility regulated byadding more or less water thereto. rFhus, by adding more water to thesolvent, the solubility of all components in the hydrocarbon mixture arereduced, but the solubility difference between the components isincreased. This effect is reflected process-wise in less contactingstages required to obtain a product of given purity. However, a greaterthroughput of solvent must be used in order to obtain the same amount ofmaterial dissolved.

As hereinbefore stated, the solvent to be used in this invention ispreferably a mixture of a hydrophilic organic solvent and water, whereinthe amount of water contained in the mixture is selected to regulate thesolubility in the solvent of the materials to be separated. Suitablehydrophilic organic solvents include alcohols, glycols, aldehydes,glycerine, phenol, etc. Particular preferred solvents are diethyleneglycol, triethylene glycol, dipropylcnc glycol, tripropylene glycol andmixtures thereof containing from about 2% to about 30% by weight ofwater.

In classifying hydrocarbon type compounds according to increasingsolubility in such a solvent, it is found that the solubility of thevarious classes increases in the fo1- lowing manner: the least solubleare the parains followed in increasing order of solubility bynaphthcncs, olens, diolefins, acetylenes, sulfur, nitrogen andoxygen-contaiu ing compounds and aromatic hydrocarbons. It may thus beseen that a charge stock which is rich in unsaturated compounds willpresent a greater problem in solvent extraction than a saturated chargestock since the unsaturated compounds fall between the paraiins andaromatics in solubility. Further diiculty, in having unsaturatedcompounds in the feed, is that they tend to polymerize at highertemperatures to form sludges and other undesirable materials. It may beseen that an ideal charge to solvent extraction is one containingparatiinic and aromatic hydrocarbons exclusively.

The -parainic compounds also differ among themselves in their relativesolubility in the solvent. appears to be a function of the boiling pointof thevparafiin with the lower boiling or lighter parans being moresoluble than the higher boiling or heavier parains. Therefore, whenheavy parains are dissolved in the solvent they may be displaced fromthe solvent by adding lighter parains thereto.

At least a portion of the raina-te from the extraction zone is passed tothe second reforming zone in which it is contacted with a catalysthaving dehydrocyclization and isomerizing activity. The second zone ismaintained at aromatization and isomerizing conditions. In a preferredembodiment of this invention the raiiinate, that is the nonaromatichydrocarbons separated from the extraction Zone, is fractionated in afractionation zone to separate therefrom a C@ hydrocarbon fractionboiling in the range of from about 150 F. to about 185 F. and containingtive-membered ring naphthenes, and this fraction is subjected in thesecond reforming zone to catalytic .isomerization and aromatization at apressure below about 300 pounds per square inch to form additionalaromatic hydrocarbons and isohexanes. As hereinbefore mentioned, the useof a second catalytic reaction zone is preferred since the conditions inthe second zone may be selected so as to produce the highest possibleyield of aromatics from the charge stock to the second zone. The eluentfrom the second reaction zone is passed to the rst mentionedfractionation zone, or stabilizer,ffor fractionation therein togetherwith the eluent from the first catalytic reforming zone. As hereinbeforementioned, the commingled isohexane and lighter hydrocarbons boilingbelow about 150 F. are recovered as anoverhead product i'n suchfractionation zone.

r Additional features and advantages of my invention, will be apparentfrom the following description of the accompanying drawing whichillustrates a particular method for conducting a gasoline reformingoperation in accordance with the present invention. The drawing isdescribed in conjunction with a specific example of the production of ahighly aromatic product. For the purpose of simplicity, many valves,pumps, heat exchangers, etc. have been omitted from thedrawing, sincetheir illustration is not necessary for a complete understanding of theinvention'.

vReferring now to the drawing, there is indicated a 150 F. to 400 F.gasoline charge stream being passed by way of line 1 and valve 2 into aheater 3 while in admixture with a hydrogen stream being introduced byway` of line 4. This gasoline stream may be a straightrun gasoline,natural gasoline or other relatively low octane number stream Which isto undergo reforming to provide a high yield of aromatic hydrocarbons,together with desirable high octane number aviation and motor fuels. Aheated stream, at a temperature of the order of about 920 F., or withinthe range of 900 F. to 950 F., while at a pressure of the order of 600pounds per square inch or Within the range of from about 300 to about1000 pounds per square inch, is introduced by way of line 5 into reactor6. Reforming'reactor 6 contains a bed of spherical catalyst ofapproximately 1s-inch average diameter, containing about 0.375%platinum, 0.5% combined fluorine, and 0.1% combined chlorine. During thepassage of the chargingstock through the rst reactor 6, the bulk of thenaphthenes containing six or more carbon atoms per molecule, aredehydrogenated to the corresponding aromatics and a portion of theparafns are hydrocracked to lower boiling paraiiins. lsomerization ofthe parains and .dehydrocyclization of theparafns in the chargepreferably also take place. The drawing indicates a single conversionkzone 6, however, it is to be understood that one or more zones may beutilized in series, with interheaters therebetween if desired, so thatthere may be accomplished a substantial degree of aromatization of thecharge stream. The conditions inthe reforming zone,

The solubilityy 10 or reactor 6, are selected so that Vsubstantially nooleni substances are produced.

catalyst of this process, oleiinic materials will not be pro duced inany appreciable amounts.

The resulting reformed stream passes from the first reaction zone 6 byway of line 7, cooler 8, line 9 and. subsequently enters a separatingzone 10'. A resultingv hydrogen-containing gaseous stream is dischargedfromA the upper portion of separating zone l10 by way of line is passed4from separator 10 by Way of yline 16 and valve 17 and enters a rstfractionation zone or stabilizer 18. ln accordance with the presentinvention, normally gaseous hydrocarbons are removed overhead throughline Z0. ln stabilizer 18, the normally gaseousy material, whichincludes hydrogen, ammonia, hydrogen su-lde, and hydrocarbon gasescontaining from 1 to 4 carbon atoms per molecule, is separated from thehydrocarbon liquid` comprising aromatic hydrocarbons and paraffinichydro' carbons.

The gaseous material passes overhead through line 20y into cooler 21,wherein a portion of the material is condensed, and the entire streampasses through line 22 into receiver 23. ln receiver23, the liquid phaseand the gaseous phase of the overhead material separate; thel gaseousmaterial passes through line 25; from which it may be vented to theatmosphere or used as fuel, or may' be further used in the presentprocess or other processes. The stabilizer has heat provided thereto byreboiler 27 and connecting lines 26 and 28. The stabilizer and receiverare 'operated at a sufficient pressure to liquefy at least a portion ofthe overhead material so that a liquid reflux stream may be availabe-toimprove the separation in stabilizer 18. The liquid redux is removedfrom receiver 23 through line 24 and passes into an upper portion ofstabilizer 18. l

The stabilizer bottoms, which as hereinbefore stated, comprisessubstantially parainic and aromatic hydro* carbons, are withdrawn fromstabilizer 18 through line 29 and are passed to an intermediate portionof a second fractionation zone or fractionator 30. In fractionator 30,the stabilizer bottoms is separated into a light overhead and heavierbottoms fraction. The conditions in fractionator 30 are maintained sothat components which are lighter than those which are preferred to bereformed in a second reactor zone are removed as an overhead fraction.ln the embodiment of the drawing, the overhead` comprises componentsboiling below normal hexane or from the boiling point of isohexanes andlighter hydrocarbons, i.e.' boiling below about 150 F.; column 30 may bereferred to as a deisohexanizer. The light hydrocar bon stream isremoved from fractionator 30 and passes throughl line 31 into cooler 32wherein the material is condensed and the entire stream passes throughline 33 into receiver 34. The liquid in receiver 34 is withdrawn throughline 35. Line 35 splits up into several streams. A portion of the streamin line 35 passes through line 36 into the upper portion of:fractionator 30 as redux. A

portion of the liquid in line 35 may be withdrawn as product throughline 37 and in some instances may be combined with the product in line113. Heat is provided to the fractionator 30 by reboiler 41 andconnecting lines 40 and 42. The bottoms, which are substantially free ofcomponents boiling below normal hexane, are removed` from thefractionator 30 through line 44 and are introduced to a lower portion ofextractor 38.

In extractor 38, the hydrocarbon material rises and is countercurrentlycontacted at an elevated temperature` At the conditions herein-1v beforespecified, and in the presence of hydrogen and the" 1 1 of 250 F. with adescending stream of selective solvent. In this embodiment 92.5%diethylene glycol and 7.5% water is used, with the solvent streamentering the upper portion of extractor 3S through line 46. Water mayalso be introduced into extractor 38 through line 69 and valve 70 whichis shown as being added to the glycol stream in line 46; however, thewater may also be added to eX- tractor 38 independently of line 46, thatis, it may be separately fed into extractor 38. As hereinbeforementioned, the water is added to increase the selectivity of thesolvent. The pressure on the column is l() p.s.i.g. The solvent to feedratio is 5:1.

As a result of the countercurrent contact of the selective solvent andthe hydrocarbon charge stock, the aromatic hydrocarbons contained in thecharge to the extractor are selectively dissolved in the solvent,thereby forming an extract stream containing the solvent and aromatichydrocarbons, and a ranate stream containing the paratfrnichydrocarbons. The rafinate stream passes from the upper portion ofextractor 38 through line 4S while the extract stream passes through thelower portion of extractor 38 through line 47. Line 47 passes to flashdrum 48. Flash drum 48 is maintained at a pressure lower than theextractor and preferably is kept atV about atmospheric pressure. In theflash drum, some of the light parafnic components are flashed overheadand are removed through line 49. The remainder of the liquid iswithdrawn from ash drum 48 through line 50 and introduced to stripper 51wherein the dissolved aromatic yhydrocarbons and dissolved paraflns areseparated from the selective solvent. Line 50 is preferably connected tothe stripper 51 at a point in the upper half of the column. Theseparation in stripper 51 is not dicult due to the fact that thearomatic hydrocarbons are substantially different in nature from theselective solvent as well as having a substantially different boilingpoint. The aromatic hydrocarbon stream along with some light paraflinspasses overhead from the stripper 51 through line 52 and combines withthe overhead from the ash drum in line 49 and the combined stream inline 53 may be passed to extract rectier 54. Heat is provided for thestripping operation by reboiler 56 and connecting lines 5S and 57. Thesolvent stream is taken from the bottom of stripper 51 through line 46and is passed into the upper portion of extractor 38 as hereinbeforementioned.

The combined stream in line 53 may be used as the final product or itmay be subjected to further treatment in order to produce a product ofhigher quality. In the present illustration the combined stream in line53 is introduced to an intermediate portion of extract rectilier 54. Inextract rectiiier 54 the lighter components, chiefly the dissolved lightparans, are removed overhead through line 53 while the aromatics areremoved from the lower portion through line 113. The gaseous material inline 58 passes through cooler 59 wherein the gaseous fraction isliqueed, and from the cooler 59 the fraction passes through line 60 andinto receiver 61. A portion of the liquefied overhead stream in receiver61 is withdrawn through line 62 and passed through line 63 into theupper portion of extract rectifier 54 as reux, and a portion of theliquefied product is withdrawn from receiver 61 through lines 62 and 64,which portion is recycled and introduced to the extractor 38 at a pointinthe lower half thereof. A portion of the liqueed product in line 62may also be removed as product through line 62. Heat is provided toextract rectifier 54 by reboiler 111 with connecting lines 110 and 112.

The rainate stream from extractor 3S, which is withdrawn through line45, may be passed directly t0 the second reforming operation in reactor91. However, it is preferred that the rainate stream be further treatedin order to improve its suitability for recycling to the reformingreactor. The rainate contains dissolved and entrained solvent andfurther the raffinate may contain 12 components which may be heavierthan are suitable for reforming.

In the drawing the ranate in line 45 is introduced into glycol separator72. Separator 72 may be a type of holding or settling tank wherein theglycol Aentrained in the raffinate is allowed to settle out of therainate phase. Separated solvent is removed from separator 72 by way ofline 73 and the remaining rainate stream is withdrawn from separator 72through line 74 and subjected to a water wash in vessel 75. The waterwas column 7S is illustrated as a vertical vessel in which the rainateis introduced at a lower portion thereof, and is couutercurrentlycontacted with a descending stream of water introduced to column 75 inthe upper portion thereof through line 76. The water and solvent areremoved frorn vessel 75 through line 78, and the washed raffinate isremoved from the upper portion of the vessel through line 77. A portionof the washed rafnate may be removed from the system through line 77acontaining valve 78b. In one embodiment of the invention, valve 78' inline 77 is maintained closed and valve 78" inline 77' is maintainedopen. The raffinate in line '77 thereby continues through line 77' andopen valve 73" into line' 85. In a preferred embodiment hereinbeforedescribed, valve 78" is maintained closed and valve 78 is maintainedopen. The raiinate in line 77 thereby continues through open valve 78and into fractionator 79. Fractionator 79 has heat provided thereto byreboiler 87 and connecting lines 86 and 88. In fractionator 79 the nonaromatic hydrocarbon stream undergoes separation to provide an overheadstream having an atmospheric b0iling range of F. to 185 F., and in viewof the previous separation made in fractionator 50, this overheadfraction comprises primarily selected C6 hydrocarbons. The overheadmaterial is withdrawn through line 80, passes through cooler 81 and line82 into overhead receiver 83. The receiver 83 and fractionator 79 areoperated so as to liquefy the overhead material. At least a portion ofthe 15G-185 F. fraction in receiver 83 is returned to an upper portionof fractionator 79 through line 84 as redux. The bottoms from the column79, which -boil above about F., provides a gasoline stream suitable formotor fuel blending. This latter stream is indicated as being withdrawnby way of line 89.

The aforementioned overhead cut, boiling inuthe range of from about 150F. to about 185 F., is removed from receiver 83 through line 85. Thehydrocarbon in line 85 mixes with hydrogen introduced in line 90 and themixture of hydrocarbon and hydrogen in line 91 passes into heater 92wherein the combined stream is heated to a temperature of the order ofabout 920 F. or within the range of 900 F. to 970 F. The pressure in thesecond reaction zone is 290 pounds per square inch.l

The combined stream in heater 92 passes through line 93 into reactor 94.Reforming reactor 94 contains a bed of spherical catalyst of the samecomposition as the catalyst in reactor 6. During the passage of thecharge stock through the second reactor 94, a substantial portion of theparafins are hydrocracked to lower boiling parains. A substantialportion of the parafns are also isomerized; for example, normal hexaneis isomerized to isohexane. Naphthenes are also dehydrogenated toaromatics, for example cyclohexane is dehydrogenated to benzene. C6hydrocarbons containing ive-membered ring naphthenes are also isomerizedand aromatized to aromatics, for example, methylcyclopentane isconverted to benzene. The drawing indicates a single conversion zone 94,however, it is understood that one or more zones may be utilized inseries with interheaters between as desired so that there may beaccomplished a substantial degree 0f conversion of the charge stream.The conditions in the reforming zone or reactor 94 are selected so thatthere is substantial conversion of parains and cycloparains to aromaticsand so that there are substantially no olenic substances'produced. Atthe conditions here-` inbefore specified, and in4 the presence ofhydrogen. and' The resulting reformed stream passes from second reaction zone 94 by way of line 95, cooler 96 and line 97 containing valve987and subsequently enters a separating zone or receiver 99. A resultinghydrogen-containing gaseousfstream is discharged from the upper portionofthe separating zone 99 by way of line 100 and a portion of this streammay ybe vented or withdrawn as fuel gas or process gas by way of line101 containing valve 102, while the remaining portion passes intocompressor 103. The compressor 103 provides a recycling of a portion ofa hydrogen-containing stream by way of line 90. The condensedhydrocarbon stream is Iwithdrawn from separator 99 by way of line104,-valve 105, and line 19. Line 19 introduces the liquid into thefirst Afractionation zone or stabilizer 18.

Although the-process illustrated in the drawing represents one of thepreferred -forms of my invention, it i's to be understood that myinvention is not limited thereby. A number of variations may beintroduced into the process without departing from the spirit or scopeof said invention.

I claim as my invention:

l. A process whichv comprises catalytically reforming a gasolinefraction at a pressure of from about 200 to about 1000 pounds per squareinch, separating from the'resultant products a low-boiling fractioncontaining isohexane and lighter hydrocarbons and a heavier fractioncontaining aromatics, normal hexane and live-membered ring naphthenes,subjecting said heavier fraction to solvent extraction to separate thearomatics therefrom, and catalytically reforming the remainingnon-aromatic raimate, comprising normal hexane and Ve-membered ringnaphthenes, at a pressure at least 75 pounds per square inch lower thanthat in the iirst-mentioned reforming step to form a product containingadditional aromatics and isohexane.

V2.. A process which comprises catalytically reforming a gasolinefraction-at a pressure of from about 200 to about 1000 pounds per squareinch, separating from the resultant products a low-boiling fractioncontaining isohexane and lighter hydrocarbons and a heavier fractioncontaining iive-membered ring naphthenes, normal hexane and aromatics,subjecting said heavier fraction to solvent extraction to separatearomatics from paratiins, fractionating the resultant parainic raiiinateto separate therefrom a C6 fraction having an atmospheric boiling rangeof from about 150 F. to about 185 F. and containing normal hexane andve-membered ring naphthenes, and catalytically reforming said C6fraction at a pressure at least 75 pounds per square inch lower thanthat in the first-mentioned reforming step to form additional aromaticsand isohexaue.

3. A process for effecting an improved yield of aromatic hydrocarbonsfrom a hydrocarbon stream boiling within the gasoline boiling rangewhich comprises subjecting said stream and hydrogen to reforming in thepresence of a catalyst that promotes dehydrogenation of naphthenes andhydrocracking of paraflins, fractionating the resulting reformed streamand removing normally gaseous components therefrom in a lirstfractionating zone, passing the remaining stream from said firstfractionating zone to a second fractionating zone and fractionating saidstream to separate a low boiling stream containing isohexane and lighterhydrocarbons from the aromatic-rich portion of said stream, passing theremaining aromatic-rich portion to a solvent extraction zone,withdrawing from said extraction zone a fraction containing asubstantial portion of aromatic hydrocarbons and a second fractionhaving an atmospheric boiling range of from about 150 F. to about 185 F.and containing normal hexane and ve-membered ring naphthenes, subjectingsaid second fraction to dehydrocycli'zation ir'ifthepesence of hydrogenand eifecting tlr'e conversion 'thereof to formA additionalaromatichydrostream recycling at least a portion of this latter: streamto said rst fractionating zone to recover said additionalisohexane fromsaid process.

4. A process for effecting an improved yield of aromatic hydrocarbonsfrom a hydrocarbon stream boiling within the gasoline boiling rangewhich comprises subjecting said stream and hydrogen to reforming in the`presence of a catalyst comprising platinum, alumina and combinedhalogen, at conditions that promote del hydrogenation of naphthenes andhydrocracking of parans, fractionating the resulting reformed stream andremoving normally gaseous components therefrom ina rst fractionatingzone, passing the remaining stream from said first fractionating zone toa second fractionating zone,- separating a low-boiling stream containingisohex-v ane and lighter hydrocarbons from the aromatic-rich portion ofsaid stream,l passing the aromatic-rich portion. to a solvent extractionzone and countercurrently contacting said portion with a selectivesolvent vto remove a substantial portion vof the aromatics therefrom,subjecting the resulting parainic ranate, containing normal hexane andiive-membered ring naphthenes, to reforming in the presence of hydrogenand with a catalyst comprising platinum, alumina and combined halogen atdehydrocyclization conditions and a pressure at least k pounds persquare inch lower than in the rstmentioned reforming zone, effecting theconversion thereof to form additional aromatic hydrocarbons andisohexane, separating the resulting stream to provide a gaseous hydrogenstream and a hydrocarbon stream and recycling at least a portion of thislatter stream to said iirst rfractionating step to recover saidadditional isohexane from said process. 5. The'p'rocess of claim 4further characterized in that said paraliinic rainate is subjected toreforming at highertemperatures than said gasoline fraction.

6. A process forr eiecting an improved yield of aromatic hydrocarbonsfrom a gasoline stream, which com-- prises, subjecting said gasolinestream to reforming in the presence of hydrogen and aplatinum-alumina-combined halogen catalyst at a temperature of the orderof about 900 F. and a pressure within the range of from about 500p.s.i.g. to about 800 p.s.i.g., effecting the separation thereof toprovide a normally gaseous hydrogencontaining stream and anaromatic-rich hydrocarbon stream, fractionating the latter to separate alow-boiling hydrocarbon stream having an end boiling point below aboutP. and containing isohexanes and lighter hydrocarbons from saidaromatic-rich portion of the stream, passing a resulting aromatic-richstream to an extraction zone and effecting the recovery of aromatichydrocarbons therefrom, passing a resulting non-aromatic hydrocarbonstream from said extraction zone to a second fractionation zone andseparating the non-aromatic stream to provide a gasoline stream boilingabove about F. and a light hydrocarbon stream having an atmosphericboiling range of from about 150 F. to about 185 F. and containingve-membered ring naphthenes, subjecting this later stream to contactwith a platinum-alumina-combined halogen catalyst at a temperaturewithin the range of from about 700 F. to about 850 F, and at a pressureof less than about 300 p.s.i.g. and forming thereby additional aromatichydrocarbons and isohexanes, cooling and separating the latterhydrocarbon stream to provide a gasous hydrogen-containing stream and aliquid stream and recycling the latter to said iirst fractionation zoneand into admixture with the reformed hydrocarbon stream passing theretowhereby said additional isohexanes may be recovered from said processand said additional aromatics may be introduced to said extraction zone.

7. A reforming process which comprises subjecting gasoline to catalyticaromatization at a pressure in excess of about 500 pounds per squareinch, fractionating the resultant hydrocarbon products in afractionating zone to separate isohexanes and lighter hydrocarbonsboiling below about 150 F. from n-hexane and heavier hydrocarbons,subjecting said n-hexane and heavier hydrocarbons to solvent extractionto separate aromatic hydrocarbons from non-aromatic hydrocarbons,recovering the separated aromatics, fractionating said non-aromatichydrocarbons in a second fractionating zone to separate therefrom a Chydrocarbon fraction having an atmospheric boiling range of from about150 F. to about 185 F. and containing ve-membered ring naphthenes,subjecting said C3 fraction to catalytic isomerization and aromatizationat a pressure below about 300 pounds per square inch to form additionalaromatic hydrocarbons and isohexanes, supplying the resultanthydrocarbon conversion products to the first-mentioned fractionatingzone for fractionation therein together with the first-mentionedhydrocarbon products, and recovering as an overhead product frompsaidfirst-mentioned fractionating zone the commingled isohexane and lighterhydrocarbons boiling below about 150 F.

8. The process of claim 7 further characterized in that the aromatizingand isomerizing reactions are eiected in the presence of aplatinum-alumina-combined halogen catalyst.

9. A catalytic reforming process which comprises subjecting a gasolinefraction to reforming at a temperature of from about 600 F. to about1000 F. and a pressure of from about 500 to about 800 pounds per squareinch, with hydrogen at a hydrogen to hydrocarbon mol ratio of from about5:1 to about 20:1, said conditions in the reforming zone being selectedto minimize the production of olenic hydrocarbons, in the presence of acatalyst comprising alumina, 0.01% to about 1% by weight of platinum andfrom about 0.1% to about 3% by weight of combined halogen, subsequentlycooling the resultant reformed stream and effecting the separationthereof to provide a gaseous hydrogen-containing stream and anaromatic-rich hydrocarbon stream, introducing said aromatic-rich streamto a first fractionating zone to remove maining aromatic-richhydrocarbon stream from the first fractionation zone to a secondfractionation zone and fractionating said stream to separatealow-boiling stream containing isohexanes and lighter hydrocarbons,having a boiling point below about F., from the aromatic-rich portion ofsaid stream, passing the resulting fractionated aromatic-rich streamfrom the second fractionation zone to an extraction zone wherein saidstream is countercurrently contacted with a selective solvent containingdiethylene glycol and from about 2% to about 30% by weight of water,separately removing from said extraction zone an extract streamcontaining said solvent and a substantial amount of the aromatics insaid portion, and a ramnate stream containing a substantial amount ofparainic hydrocarbons, introducing said extract to a stripping column,removing as overhead from said column an aromatic-containing stream,removing as bottoms from said column a solvent stream and recycling saidstream to said extraction zone, fractionating said ratlnate to separatetherefrom a C5 hydrocarbon fraction having an atmospheric boiling rangeof from about 150 F. to about F. and containing iive-membered ringnaphthenes, subjecting said C6 fraction together with hydrogen to contact with a dehydrocyclization catalyst at a pressure below 300 poundsper square inch, effecting thereby the conversion thereof to formadditional aromatic hydrocarbons, separating the resulting stream toprovide a gaseous hydrogen-containing stream and a hydrocarbon streamand recycling at least a portion of this latter stream to the firstfractionation zone.

References Cited in the le of this patent UNITED STATES PATENTSSchneider et al Oct. 13, 1959

4. A PROCESS FOR EFFECTING AN IMPROVED YIELD OF AROMATIC HYDROCARBONSFROM A HYDROCARBON STREAM BOILING WITHIN THE GASOLINE BOILING RANGEWHICH COMPRISES SUBJECTING SAID STREAM AND HYDROGENN TO REFORMING IN THEPRESENCE OF A CATALYST COMPRISING PLATINUM, ALUMINA AND COMBINEDHALOGEN, AT CONDITIONS THAT PROMOTE DEHYDROGENATION OF NAPHTHENES ANDHYDROCRACKING OF PARAFFINS, FRACTIONATING THE RESULTING REFORMED STREAMAND REMOVING NORMALLY GASEOUS COMPONENTS THEREFROM IN A FIRSTFRACTIONATING ZONE, PASSING THE REMAINING STREAM FROM SAID FIRSTFRACTIONATING ZONE TO A SECOND FRACTIONATING ZONE, SEPARATING ALOW-BOILING STREAM CONTAINING ISOHEXANE AND LIGHTER HYDROCARBONS FROMTHE AROMATIC-RICH PORTION OF SAID STREAM, PASSING THE AROMATIC-RICHPORTION TO A SOLVENT EXTRACTION ZONE AND COUNTERCURRENTLY CONTACTINGSAID PORTION WITH A SELECTIVE SOLVENT TO REMOVE TO A SUBSTRANTIALPORTION OF THE AROMATICS THEREFROM, SUBJECTING THE RESULTING PARAFFINICRAFFINATE, CONTAINING NORMAL HEXANE AND FIVE-MEMBERED RILNG NAPHTHENES,TO REFORMING IN THE PRESENCE OF HYDROGEN AND WITH A CATALYST